Did tune up and lowered my gas mileage... sweet!

[MagicRat]

Originally Posted by Airjer_

That's not bad advice, we didn't know where he road tripped and he is from Iowa and the temps have been cooler in the upper mid-west lately have they not?

I think we can all agree that there is not one problem that is contributing to a ten MPG drop in fuel economy. As we poke and prod we start finding out little bits and pieces that start to reveal that there are several things that are not right. Had I not suggested that temp may be a factor we may have not know he went to Dallas which was revealed a couple posts later!

In that case, you are still making the wrong suggestions. Instead on making broad, sweeping generalizations about air temp, you should address relevant issues.
It's not the cold temps, per se, that make the difference, its the driving style, the car's T-stat condition etc that is relevant.

So,,, lets ask.


Was the 1800 mile trip performed in lots of little hops, or was it mostly steady highway miles?
Also does the car have a temp gauge? Is it running at a normal temp, or pretty cool?

[chopsieze]

Originally Posted by Airjer_

That's not bad advice, we didn't know where he road tripped and he is from Iowa and the temps have been cooler in the upper mid-west lately have they not?

I think we can all agree that there is not one problem that is contributing to a ten MPG drop in fuel economy. As we poke and prod we start finding out little bits and pieces that start to reveal that there are several things that are not right. Had I not suggested that temp may be a factor we may have not know he went to Dallas which was revealed a couple posts later!

I haven't done any changes to the car for the last couple years other than oil and air filter changes till just before my trip. The car has been great on gas... yes I know the colder weather will decrease mpg but once your car is warm shouldn't be much of a factor. I notice a loss but 2-3mpg in the winter if I'm doing more 10 min trips but when I'm commuting (even in the winter) it's always been about the same. I drive this car almost every day and calculate the mileage every tank... unless my wife fills up the car cause she doesn't ever reset the gauge.

Me going to Dallas shouldn't have much effect, and if it did it should have improved my mpg.

[chopsieze]

Originally Posted by MagicRat

In that case, you are still making the wrong suggestions. Instead on making broad, sweeping generalizations about air temp, you should address relevant issues.
It's not the cold temps, per se, that make the difference, its the driving style, the car's T-stat condition etc that is relevant.

So,,, lets ask.


Was the 1800 mile trip performed in lots of little hops, or was it mostly steady highway miles?
Also does the car have a temp gauge? Is it running at a normal temp, or pretty cool?

The car was driven straight there and straight back... sat for a 2 days while I was there. I've taken it on many trips and usually average 70mph on the interstates and have hit close to 40mpg... this time not so.

The stat seemed to be lower than I remember it. I remember it usually being slightly below the mid point but this time it wasn't even close... I'm thinking it's part of my problem. Want to check plugs too. Can anyone tell me what a 96 Prizm 1.8l gap should be?

[akboss]

Originally Posted by Airjer_

Your car isn't rated for 51 psi! Every tire manufacturer and every vehicle manufacture tells you to inflate the tire to the vehicle NOT what it says on the tire! The amount of savings you get in fuel economy are not worth the sacrifices you make in safety. An over inflated tire reduces the footprint of the tire which results in a decrease in traction. During an emergency maneuver you may find the tires skipping or skidding instead of responding to you command to turn! over inflation also will result in greater breaking distance. For that small of a car 51 psi is grossly overinflated!

You said you haven't had those tires on since the last road test?

Agreed - max pressure isn't the recommended operating pressure. As your tires heat up over the course of normal driving the air inside expands, potentially causing a nasty blowout - at 55+ psi, that wouldn't be pretty. Typically road tires are inflated at 32psi, maybe 35.

The money saved by lower rolling resistance on overinflated tires is inconsequential compared to the excess wear caused on your tires - save $5 in fuel to spend $400 on a new set of shoes, not to mention the safety risks.

[akboss]

Originally Posted by chopsieze

Can anyone tell me what a 96 Prizm 1.8l gap should be?

Check your owner's manual, should be there. If you don't have one, there should be a sticker under your hood.

[chopsieze]

Originally Posted by Airjer_

Your car isn't rated for 51 psi! Every tire manufacturer and every vehicle manufacture tells you to inflate the tire to the vehicle NOT what it says on the tire! The amount of savings you get in fuel economy are not worth the sacrifices you make in safety. An over inflated tire reduces the footprint of the tire which results in a decrease in traction. During an emergency maneuver you may find the tires skipping or skidding instead of responding to you command to turn! over inflation also will result in greater breaking distance. For that small of a car 51 psi is grossly overinflated!

You said you haven't had those tires on since the last road test?

This topic is a huge, heated debate. I don't fill my tires full to max 51psi... I understand it's the max, tires heat up when driven, etc.

There have been plenty of tests done on traction, mpg and wear that shows benefits to higher psi. Also I understand about car ratings and tire ratings. I lean to the tires, and use there rating for proper footprint, etc. The only info I haven't found much on in the argument is braking.

I don't really want to get into this, I think Ford and Firestone got into it and doesn't seem like there is ever going to be one way to think when it comes to the subject. Safety, mpg, wear... can all be argued either way, even blowouts and temp can be argued one way or the other. I'm not a hard core either way, I just lean to the tire ratings. I'd say 80% of people air to what's on the tire not the door jamb so it can't be all that bad.

[chopsieze]

Originally Posted by akboss

Check your owner's manual, should be there. If you don't have one, there should be a sticker under your hood.

Someone broke into the car years ago and took the manual and funny enough not the money in the ash tray. I looked under the hood but will look again. They told me at the auto parts store it was .032 but they didn't seem too sure at the time. I'll look at the originals and more online, may have to go to the library and get a chilton's.

[akboss]

That sucks you got broken into - some people just suck. My bro had his Honda parked at a mall with some Christmas gifts in the back for his wife/family (this was late December) and some guy figured he'd smash through the window and take all the gifts, and the CD deck. People are so thoughtful! I guess you hope it went to someone who needed it more, but more than likely it funded a bottle of JD's.

[blazee]

Originally Posted by Airjer_

Your car isn't rated for 51 psi! Every tire manufacturer and every vehicle manufacture tells you to inflate the tire to the vehicle NOT what it says on the tire! The amount of savings you get in fuel economy are not worth the sacrifices you make in safety. An over inflated tire reduces the footprint of the tire which results in a decrease in traction. During an emergency maneuver you may find the tires skipping or skidding instead of responding to you command to turn! over inflation also will result in greater breaking distance. For that small of a car 51 psi is grossly overinflated!

You said you haven't had those tires on since the last road test?

Originally Posted by akboss

Agreed - max pressure isn't the recommended operating pressure. As your tires heat up over the course of normal driving the air inside expands, potentially causing a nasty blowout - at 55+ psi, that wouldn't be pretty. Typically road tires are inflated at 32psi, maybe 35.

The money saved by lower rolling resistance on overinflated tires is inconsequential compared to the excess wear caused on your tires - save $5 in fuel to spend $400 on a new set of shoes, not to mention the safety risks.

Originally Posted by chopsieze

This topic is a huge, heated debate.

It's not actually a huge debate at all. There is a right way and a wrong way. Using the tire spec is the wrong way. The only reason to use the tire spec, is to check to make sure the tire can handle the vehicle manufacturer's PSI rating. In the rare instances that the vehicle has a higher spec than the tire, then a different tire must be used.

Originally Posted by chopsieze

There have been plenty of tests done on traction, mpg and wear that shows benefits to higher psi. Also I understand about car ratings and tire ratings. I lean to the tires, and use there rating for proper footprint, etc. The only info I haven't found much on in the argument is braking.

Actually, if you understood anything about car and tire ratings, you would know that it is impossible for the tire manufacturer to give you a spec for the proper footprint. The footprint is is determined solely by the PSI and the weight of the vehicle. 35 pounds per square inch, for example, means that every square inch of the tire in contact with the ground is supporting 35lbs. So, for a vehicle that weighed 3500lbs, there would be a total of 100 square inches of tire in contact with the ground (approximately 25 square inch footprint per tire depending on weight distribution). Whether or not this footprint is safe, depends on the size of the tire. That is why the car manufacturer gives you a tire size spec, and a PSI spec.

The tire manufacturer has no idea what vehicle their tires will be used on, nor the weight and therefore do not attempt to tell you what pressure to run. The pressure on the tire simply tells you the amount of weight (the size of the tire and the PSI are the two determining factors in the amount of weight that it can support, and limited by the quality of the construction) that it can support to make sure that you don't over load it. It is in no way intended to tell you what is safe for your particular vehicle.

[Airjer_]

What brand of plugs did you install?

OOOOps I see they where NGK's....never mind.

The book says the original plug was a standard copper core #BKR5EKB-11 with an .044 gap. NAPA lists the standard and v-power as O.E with a .042 gap. Mitchell also lists the standard NGK with a gap spec of .043. Would it be possible for an improperly gapped and/or V-power plug to have some effect on fuel economy? Where the plugs you took out also v-powers?

[Stealthee]

Originally Posted by Airjer_

When temps drop from 80 degrees to -20 degrees Fahrenheit it makes a huge difference in overall fuel economy. just the amount of energy to get everything moving on a cold morning will suck your tank dry! I can go from 34-35mpg on the freeway in the Saturn in the summer on the freeway at 70 mph to 28-29mpg under the same circumstances only 80 to 100 degrees colder. So if you want to come to Minnesota on a nice crisp winter morning we'll give your theory a shot but I can tell you it won't hold water!

You do realize its not the colder weather that affects gas mileage, its the different fuel mixes between summer and winter.

[chopsieze]

Originally Posted by blazee

It's not actually a huge debate at all. There is a right way and a wrong way. Using the tire spec is the wrong way. The only reason to use the tire spec, is to check to make sure the tire can handle the vehicle manufacturer's PSI rating. In the rare instances that the vehicle has a higher spec than the tire, then a different tire must be used.

Actually, if you understood anything about car and tire ratings, you would know that it is impossible for the tire manufacturer to give you a spec for the proper footprint. The footprint is is determined solely by the PSI and the weight of the vehicle. 35 pounds per square inch, for example, means that every square inch of the tire in contact with the ground is supporting 35lbs. So, for a vehicle that weighed 3500lbs, there would be a total of 100 square inches of tire in contact with the ground (approximately 25 square inch footprint per tire depending on weight distribution). Whether or not this footprint is safe, depends on the size of the tire. That is why the car manufacturer gives you a tire size spec, and a PSI spec.

The tire manufacturer has no idea what vehicle their tires will be used on, nor the weight and therefore do not attempt to tell you what pressure to run. The pressure on the tire simply tells you the amount of weight (the size of the tire and the PSI are the two determining factors in the amount of weight that it can support, and limited by the quality of the construction) that it can support to make sure that you don't over load it. It is in no way intended to tell you what is safe for your particular vehicle.

It actually is a big debate that I've spent quite a bit of time reading and talking to people about... you can go on google or car forums and find plenty of discussion. Most people tend to side with the car rating and I'm not going to claim to be an expert or even say who's wrong. I just believe most car manufactures want a smooth ride and lower psi is going to give them that. I don't know what the dangers are , I believe the footprint is effected by the weight and when I put air in my tires it's with the car on the ground. I think you would have to significantly go over the max also to be dangerous. New steel belted radials will pop much easier and more often with not enough air than more (that's not even a debate).

I do think it's a good idea to match tire speeds, etc with your car but I still think if you aren't as concerned about a soft ride, want better performance, mpg and handling (including traction) and less chance of hydroplaning then higher psi is better (obviously I don't mean extreme). I believe the footprint of any tire will be best as long as it's under the max psi on the tire with the load on the tire, but (serious ?) do tires have a recommended psi for proper footprint?

Not trying to argue, I'd like to hear what real dangers there are. I do know a tire will not exploded from pressure at 50psi. Max tire pressures (I've always thought, and either cold or hot there could be such a swing since 10 degrees changes about 1 psi) are for a cold tire, the tire manufactures take into consideration heat from speed and being on the road and it's actually much higher then stated. I think I saw a youtube video of a car tire holding close to 200psi and hear of one getting to 250 before it popped. I'm only saying what is my opinion, you guys might change my mind. I tend to go for the underdog, but I feel like this is another situation where someone made me think outside the box and they made some pretty good points and I went with it.

Here's an article I found in 2 seconds looking on google from a Police Sgt. with EVOC (Emergancy Vehicle Operator Course), not the greatest one to use as in an argument, I've read many more scientific, physic related articles but just shows you that there's others thinking the way I am and they've actually done tests.

http://www.funbolt.com/articles/toyo...pective-67139/

[chopsieze]

Originally Posted by Airjer_

What brand of plugs did you install?

OOOOps I see they where NGK's....never mind.

The book says the original plug was a standard copper core #BKR5EKB-11 with an .044 gap. NAPA lists the standard and v-power as O.E with a .042 gap. Mitchell also lists the standard NGK with a gap spec of .043. Would it be possible for an improperly gapped and/or V-power plug to have some effect on fuel economy? Where the plugs you took out also v-powers?

Thanks a bunch for that info. I got NGK V-power plugs (copper). I think my gap is way off and will split the diff and set to .043 I guess. I looked at the old plugs and they're wore down and the gap is about .060 on them now.

[akboss]

Originally Posted by chopsieze

Not trying to argue, I'd like to hear what real dangers there are.

First article I found from a major publication (Wheels.ca):

http://www.wheels.ca/Tire%20Talk/article/415271

First Paragraph:

"There has been much bunk posted on the Internet about how easy it is to save fuel by over-inflating the tires on a vehicle. The people never mention the downside: driver safety."

[chopsieze]

Originally Posted by Airjer_

What brand of plugs did you install?

OOOOps I see they where NGK's....never mind.

The book says the original plug was a standard copper core #BKR5EKB-11 with an .044 gap. NAPA lists the standard and v-power as O.E with a .042 gap. Mitchell also lists the standard NGK with a gap spec of .043. Would it be possible for an improperly gapped and/or V-power plug to have some effect on fuel economy? Where the plugs you took out also v-powers?

airjer, I was wondering if you could look up the thermostat temp I'm supposed to run? Thought it was 180 but the have 195's that fit my car too.

Thanks!